Forget Amazon or your favorite store’s website, social networks are expanding into direct e-commerce. Facebook Inc. (NASDAQ: FB) is testing a new tab on the Facebook mobile app that adds a one-click shopping experience.

Facebook users will soon see a section called “Shopping” as the fourth tab, right below “Groups,” found in the “More” page of the Facebook mobile app. By clicking on the tab, users will be brought to a page where they can see sections such as "List of Fall Looks" and also a search bar.

The social network is testing with a select number of small businesses in the United States. These partners may include Jasper’s Boutique, pictured in the art on the blog post announcement.

facebook shopping Facebook has added a "Shopping" tab to the mobile app. Photo: Facebook

The update is the latest move to expand e-commerce on social networks, as they further tap into a giant online industry. Total e-commerce sales are expected to come in at $1.67 trillion in 2015, up from $1.3 trillion the previous year, according to eMarketer. Twitter Inc. (NYSE: TWTR) more widely rolled out a “Buy” button -- a system that allows click-to-purchase options -- last month. Twitter also has been testing product pages on retailers’ Twitter profiles. Google and Pinterest both have “Buy” buttons as well. So far, they do not take a revenue cut but instead charge for promoting the page with an advertisement or promoted pin.

Facebook has been moving deeper into shopping experiences and attracting more small businesses. The entry follows Facebook's emphasis on the effectiveness of its mobile app and ad products. Facebook's revenue now tops $4 billion, up 39 percent year-over-year, with 76 percent of ad revenue coming from mobile, the company reported in July.

Facebook now boasts having 45 million monthly active pages on the network. Facebook Chief Operating Officer Sheryl Sandberg is pitching her company as the essential Web presence for small businesses. In September, the site released design changes and added features, including call-to-action buttons, on Pages. These updates came after years of Facebook not innovating on the product.

“Facebook pages are the mobile Web presence for small businesses. [We want to help you] be a part of the revolution which is happening in communication,” Sandberg said in September at the launch event.

Facebook’s latest announcement of more e-commerce options also included explaining ad offerings, including the “Carousel” -- products listed in a vertical format -- and the “Canvas” -- a full-screen viewing of products like on a retailer’s page.